Electronics > Beginners

5V regulator outputting 5.9V and more.

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floobydust:
MLCC has a huge voltage coefficient of capacitance which makes them useless at the 100uF 5V level. You're lucky to get 22-30uF at room temp in 1206 i.e. TDK C3216JB1A107 datasheet

The ST datasheet graph is even worse :palm:
I hate parts like this because a second-source actually ends up being a terrible mistake in production, when supply chain assumes it's the same part number.

james_s:
You really have to be careful with MLCC, many people are blissfully unaware of how dramatically the capacitance drops with DC across them. I was also not aware of this trait until it bit me a few times, fortunately in one-off hobby projects. It usually works fine to sprinkle on a bunch of 100n decoupling caps, but if you actually try to calculate the needed capacitance it will really get you if you don't account for that.

Simon:
well my choice of part was dictated by the load dump protection. So a normal electrolytic might be better? will have to check the specs on those caps I have at work. I just need to get this working, do a demo for my course work and move on.

Simon:

--- Quote from: james_s on December 09, 2019, 07:42:10 am ---You really have to be careful with MLCC, many people are blissfully unaware of how dramatically the capacitance drops with DC across them. I was also not aware of this trait until it bit me a few times, fortunately in one-off hobby projects. It usually works fine to sprinkle on a bunch of 100n decoupling caps, but if you actually try to calculate the needed capacitance it will really get you if you don't account for that.

--- End quote ---

Yea, that's why you use 25-50V parts even at 5V

wraper:

--- Quote from: floobydust on December 09, 2019, 05:44:09 am ---The ST datasheet graph is even worse :palm:
I hate parts like this because a second-source actually ends up being a terrible mistake in production, when supply chain assumes it's the same part number.

--- End quote ---
LOL, it's almost like ESR requirements for ON semi and ST are mutually exclusive.

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